1. Field of the Invention
This invention relates to compression ignition engines or what are commonly known as diesel engines, which are conventionally designed to operate by the compression ignition of an appropriate diesel oil fuel; and to the design or conversion of such engines so as to be operable with an alternative fuel either in full substitution of the diesel oil fuel otherwise employed, or at least in the substitution of a major part of such diesel oil fuel, during normal operating conditions of the engine.
These proposals have been made for the employment of gases and liquid alcohol fuels as alternatives for spark ignition internal combustion engines and compression ignition or `diesel` engines; and while considerable success has been achieved with the employment of gaseous and liquid alcohol fuels as alternative fuels for spark ignition engines, and success to a lesser degree has been achieved with the gas conversion of diesel engines, proposals for operating diesel engines on a liquid alcohol fuel have not achieved the same degree of success. The ability to convert diesel engines to successfully and efficiently operate on an alcohol fuel such as a methanol is affected by the fact that such alcohol fuels do not spontaneously ignite in the combustion chamber of a typical diesel engine. This problem may be overcome by modification of a diesel engine to provide for spark ignition of fuel in a supplementary small combustion chamber connected to a main combustion chamber of a diesel engine; but problems have arisen in the development of this system and the system does involve substantial modifications to the basic engine and associated component design, and the adoption of such a system as a whole is not considered at present to be a viable commercial proposition.
2. Description of the Prior Art
An alternative recently developed system for diesel engines has involved the proposal to employ a pilot fuel such as an ether having a wider inflammability range and lower ignition temperature than the principal alternative alcohol fuel, and this system forms the basis of the present invention.
Reference is made to U.S. Pat. No. 4,422,412 (Norton - assignor to A.E.C.I.Limited) which relates to a device for converting an alcohol to an ether when fitted to a compression ignition engine, the device comprising a heat exchanger having an inlet to receive the alcohol and an outlet in communication with the inlet end of a catalytic conversion chamber which contains a catalyst for conversion of an alcohol to an ether. The conversion chamber has an outlet pipe to lead the ether to a cylinder of a compression ignition engine. Alcohol is fed from a storage tank along lines and direct to the cylinder and also along a line to a heat exchanger.